The invention relates to an assembly consisting of a backrest and an airbag module.
The backrest is part of a vehicle seat and comprises a frame, a padding and a covering part. The airbag module comprises an ejection channel that is attached to the frame and serves to provide a restraining effect for a vehicle occupant, especially in case of a side impact. For this purpose, an airbag folded in the airbag module is filled with compressed gas so that it unfolds at the side of the backrest between the upper torso and, if necessary, the head of the vehicle occupant on the one hand, and the door or side structure of the vehicle on the other hand.
An advantage of installing the airbag module in the backrest is that it is always fundamentally in the same position with respect to the upper torso of the vehicle occupant, regardless of whether a very tall occupant is sitting there with the seat slid all the way back or whether a very short vehicle occupant slides the vehicle seat very close toward the steering wheel or the dashboard. The disadvantage of installing the airbag module in the backrest is, of course, that the airbag module has to be accommodated in such a way that it is relatively well protected so as to prevent damage, for example, due to a load being transported in the vehicle, yet in such a way that the unfolding airbag is able to come out of the backrest without any problem. There are numerous concepts in the state of the art for purposes of fulfilling these intrinsically contradictory requirements.
DE-A-196 81 575 describes an assembly of the type mentioned above in which the airbag module is attached to the covering part of the backrest. The area of the covering part that lies against the padding is configured as a swiveling flap that swings open towards the outside, that is to say, towards the side structure of the vehicle, when the gas generator of the airbag module is activated and the airbag unfolds, so that a gap is formed between the padding and the covering part through which the airbag can emerge.
EP-A-0 776 793 describes a vehicle seat in which the airbag module is installed in a separate housing at the side in the backrest. The housing is provided with a covering flap that, when the gas generator is activated, can be pushed towards the outside by the unfolding airbag so that a gap is formed through which the airbag unfolds.
Moreover, solutions are known in which the padding of the backrest is closed by a tear-off seam that is located in the area of what will later be the gap for the deployment of the airbag and that is destroyed by the unfolding airbag.
The drawback of all of these known solutions is, first of all, that the structure of the backrest is relatively complicated and secondly that, due to the expensive design, a large number of parameters influence the unfolding of the airbag so that the unfolding process is not reliably reproducible.
The object of the invention is to improve an assembly of the type described above in such a way that an especially simple structure is achieved, which allows a reliable, consistently reproducible unfolding of the airbag.
This is achieved in an assembly consisting of a backrest and an airbag module, the backrest having a frame, a padding and a covering part. The airbag module has an ejection channel that is attached to the frame. The covering part is designed so as to be rigid whereas the padding in an area of transition to the covering part is configured so as to be so pliant that by deformation of the padding a gap is produced between the covering part and the padding, for the airbag to come out of the backrest. There are a number of advantages to this construction. For one thing, the structure of the backrest is especially simple. No special measures have to be taken to close off the gap through which the airbag emerges when it is activated, since this gap is closed by the intrinsic elasticity of the padding. Moreover, the covering part is not a component of the airbag module, so no special requirements have to be met in terms of the material properties, the design, etc. Finally, a precisely reproducible unfolding behavior is achieved since the only parameter that influences the gap for the unfolding airbag is the flexibility of the padding. The resistance that the padding offers to the unfolding airbag, however, is relatively low in any case, so that changes in the elasticity of the padding have a negligible effect on the unfolding process.
According to a preferred embodiment of the invention, it is provided that the gap is formed between the padding and the covering part in the side area of the backrest and that the ejection channel is configured so as to be curved, it extending starting from a rear side of the frame facing away from the padding toward the side area. By arranging part of the airbag module on the rear side of the backrest, the gap through which the airbag emerges can be arranged relatively close to the backrest. Due to the resultant greater distance between the outlet opening of the gas generator and the thorax region of a vehicle occupant, the airbag is rendered more suitable for restraining events in which the vehicle occupant is not seated in the position that was assumed and for which the airbag module was designed. Moreover, better sitting comfort is ensured in the lateral support region of the backrest. Furthermore, by guiding the airbag in the ejection channel, the airbag is deployed more uniformly through the gap between the padding and the covering part. The uniform deployment of the airbag through the gap is further enhanced in that the compressed gas supplied by the gas generator is thoroughly distributed as a result of the relatively large distance between the area of the airbag module into which the compressed gas flows and the gap between the padding and the covering part. Finally, the ejection channel serves as a guide for the airbag so as to prevent jamming of the airbag when it is coming out of the gap between the padding and the covering part, even if components of the vehicle intrude in this process.
Preferably, it is provided that the padding has a slanted surface lying opposite the airbag module. The slanted surface helps the padding to recede when the gas generator is activated and the airbag is unfolded, and guides the airbag out of the backrest.
According to the preferred embodiment, it is provided that the airbag module has a gas lance that constitutes the connection to a gas generator. In this manner, the gas generator can be arranged flexibly in the backrest so that, through the spatial separation of the gas generator and the ejection channel, the possibility arises to stow the airbag very compactly and to design the airbag module correspondingly compactly. Thus, they can also be used in narrow vehicles or in vehicles with a bulky side structure.
The ejection channel of the gas bag module may be formed by a housing which preferably consists of plastics and is configured in two pieces. On the side facing the outside of the seat, the housing consists of a covering and on the side facing the inside of the seat it consists of a holding part. Provision may be made that sections of the housing are moved in the nature of a flap, for opening an outlet for the emergence of the airbag.
Advantageous embodiments of the invention will be apparent from the subordinate claims.